Generously butter the pie dish, then butter each slice of brioche loaf. Top with a thick smear of marmalade. Cut each slice in half, diagonally. Arrange the triangles, corners pointing upwards in the pie dish, all facing toward you, with a few extra facing inwards around the bottom edge. Thinly slice the blood oranges then cut each slice in half. Wedge one half onto the marmalade side of each triangle of bread.
Warm the milk gently on the stove and switch it off when it starts to simmer. Put the eggs and caster sugar into a mixing bowl and whisk well, then add in the warm milk and whisk again. Pour the custard over the pudding and leave it to stand for 30 minutes.
Preheat the oven to 180C / 160C fan. Sprinkle 2-3 tablespoons of caster sugar over the top of the pudding then bake for 30 minutes, keeping a close eye on it so that the brioche and sugar don’t start to burn. Leave to stand for 15 minutes while you melt the chocolate in a microwave or in a bowl set over simmering water. Put the chocolate into a piping bag and snip a small hole in the end. Drizzle the warm pudding with melted chocolate then serve with a big scoop of vanilla ice cream.
